This invention relates to air damper apparatus particularly for heating, ventilating and air conditioning systems and particularly to improved blade end seal means for damper vanes or blades.
Heating, ventilating and air conditioning systems employ various means for controlling of the flow and distribution of air through an evironmental space to be conditioned. A highly satisfactory air flow means includes dampered openings for controlling the mixing of outside and recirculated air and the air flow from the conditioned space. For example, in systems applied to buildings, a mixture of outside and interior air is provided and, upon demand, circulated through the space to be controlled.
Generally, a conditioning unit will include an outside air damper, an exhaust air damper, and a recirculating air damper, mounted within an appropriately located duct opening for controlling of the air and air mixtures circulating through the system which further includes appropriate heating and/or cooling means, fan means and the like. Proper amounts of fresh air may be introduced into the system and a related volume exhausted from the system for positioning of the supply and exhaust dampers. In addition, face and by-pass dampers in association with the air fan units, air conditioning units, and the like are positioned to control the actual air flow into and from the environmentally conditioned space. Generally, damper units include a supporting mounting frame for mounting of the unit with respect to the flow duct opening. A plurality of interrelated blades are typically movably mounted within the framework and coupled to by a suitable mechanical linkage to a suitable common operator through an appropriate mechanical drive. Each of the blades is generally of a rectangular configuration with the longitudinal edges of adjacent blades constructed to provide an airtight seal in the closed position. A blade may be formed from a pair of opposed sheet-metal members having central portions oppositely offset to define a centrally located channel, with oppositely extending and relatively flat plate-like portions. The outer longitudinal edges are provided with an appropriate resilient sealing structure such that the adjacent blades cooperate with each other in defining effective seals in closed position. Pivot pins or shafts are located or secured in the channel portion with the pivot axis in a common plane through the plane of the edge seals. The blade edges may be provided with resilient rubber members which, in the closed position, provide a highly effective airtight seal. The blades have the end pivot pins or shafts pivotally mounted in the opposite side frame members of the rectangular frame. The top and bottom members of the frame which extend parallel to the blades are readily constructed to cooperate with the edges of the associated endmost blades to define an airtight connection in the closed position. In addition, however, the edges of the several blades should be effectively sealed to the opposite side frame members of the frame in the fully closed position of the damper unit to establish and maintain effective control of the air flow. The effective sealing of the ends of the blades, however, is complicated by the construction of the blades. Thus, sheet metal blades with appropriate ribbing or channeling to establish the desired, effective structural strength define a plurality of end edges. Although the end edges can be formed as relatively flat members, as a practical matter, the mounting of the blades may be such that the axis of adjacent blades are not in exact parallel relation. The edges of the blades will not then lie exactly in a single common plane. An effective seal may be provided by employing a pressure-type seal means. However, the seal means design should not create undue operating load on the damper operator during the initial opening or final closing of the damper unit.
Resilient rubber-like seal structures have, for example, been suggested. A continuous rubber-like member is secured within the side frame members in abutting sealing engagement with the blade ends. The rubber-like seal can move relative to blade sealing edges to close any spaces created by misalignment of the blades. However, to compensate for misalignment and the like, relatively heavy loading of the operator often occurs during the initial opening or final closing of such a commercially practical unit.
In an alternate construction each end structure is a single elongated wall or place which is mounted within the frame and extends along the length of each frame member. The plate is provided with appropriate openings for the blade pivot pins or shafts and is constructed with a channel shape to deflect into sealing engagement with the edges of the blades. Such an elongated plate can be constructed to minimize the loading on the blades. However, optimum sealing is not created if the mounting of the blades is not rather precisely controlled to maintain the ends of all of the several blades in essentially a single common plane. If the initial mounting of the blades or if the use results in any significant misalignment or angular orientation of one blade with respect to the next, the end edge of that blade is canted or angularly displaced with respect to the sealing plate. Although the sealing plate has some degree of flexibility, the plate tends to be displaced longitudinally about the canted end resulting in leakage within the end structure, generally within the aligned blade and more significantly within adjacent blades.
In the practical construction and use of the damper ventilating units, the various structures have been a compromise based on the various factors and specifications for any given installation. The existing damper units thus do provide reasonably effective control, but there is a distinct need in the art for improving the end sealing means and thereby creating more optimum air flow control.